RTCB is essential for early mouse embryogenesis.

Area of Science:

• Developmental Biology
• Molecular Biology
• Genetics

Background:

• RNA 2',3'-cyclic phosphate and 5'-OH ligase (RTCB) is a conserved RNA ligase with known physiological roles.
• The specific function of RTCB in mammalian reproduction and early embryogenesis remains largely unexplored.

Purpose of the Study:

• To investigate the role of RTCB in mouse embryonic development, particularly during gastrulation.
• To elucidate the molecular mechanisms underlying RTCB's function in early embryogenesis.

Main Methods:

• Generation of a conditional Rtcb knockout mouse model using the Ddx4-Cre system.
• Histology, immunohistochemistry, and quantitative PCR for analyzing embryonic tissues.
• Analysis of published single-cell RNA sequencing (scRNA-seq) data.
• NIH 3T3 cell experiments to assess mRNA stability upon Rtcb knockdown.

Main Results:

• Complete absence of viable Rtcb-/- offspring indicated embryonic lethality before birth.
• Rtcb knockout led to gastrulation failure around embryonic day 6.5 (E6.5).
• Gastrulation failure was associated with reduced cell proliferation and increased apoptosis.
• NUSAP1 (nucleolar and spindle-associated protein 1) mRNA stability was affected by Rtcb levels, suggesting NUSAP1 acts downstream of RTCB.
• A spatiotemporal coordination was observed between transcription factor YY1 (Yin-Yang-1), Rtcb, and Nusap1 during early embryogenesis (E3.5-E7.5).

Conclusions:

• RTCB is indispensable for successful early mouse embryogenesis.
• A novel regulatory axis involving YY1, RTCB, and NUSAP1 is proposed to maintain adequate cell proliferation for gastrulation.
• Disruption of this YY1-RTCB-NUSAP1 pathway leads to gastrulation failure and embryonic lethality.